esophageal achalasia disease

achalasia endoscopy esophageal botulinum toxin injection treatment esophagus stomach sphincter vector anatomy disease lower acid medicine muscle closed reflux junction myotomy procedure surgery relaxed trachea throat endoscope gastrointestinal system digestion regurgitation illustration block problem narrowing disorder difficult food swallowing mouth nerve paralyzed squeeze collects swallow dysphagia stuck intestine hernia botox